Radiation curable coating compositions

ABSTRACT

Coating compositions comprising a liquid vehicle, a colorant and a photosensitizer containing the structural group

United States Patent [191 Sandner et al.

[111 3,801,329 [451 Apr. 2, 1974 RADIATION CURABLE COATING COMPOSITIONS [75] Inventors: Michael Ray Sandner; Claiborn Lee Osborn, both of Charleston, W. Va.

[73] Assignee: Union Carbide Corporation, New

York, NY.

[22] Filed: Oct. 31, 1972 [21] Appl. No.: 302,574

Related US. Application Data [63] Continuation-impart of Ser. No. 209,066, Dec. 17,

[56] References Cited UNITED STATES PATENTS 3,715,293 2/1973 Sandner et a1. 204/159.14

Heine et a]. 204/159.23 Fuhr et a1. 204/159.23

Primary ExaminerNorman G. Torchin Assistant Examiner-Edward C. Kimlin Attorney, Agent, or FirmFrancis M. Fazio [5 7] ABSTRACT Coating compositions comprising a liquid vehicle, a colorant and a photosensitizer containing the structural group in which R is an alkyl or aryl group and R is hydrogen, alkyl, aryl, or cycloalkyl.

47 Claims, 4 Drawing Figures RADIATION CURABLE COATING COMPOSITIONS This application is a continuation-in-part of Ser. No. 209,066, filed Dec. 17, 1971.

BACKGROUND OF THE INVENTION Many photosensitizers are known for the radiation curing of coating compositions or the polymerization of vinyl monomers. These fall into many classes and include compounds such as acetophenone, propiophenone, benzophenone, xanthone, fluoroenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-or 4-methylacetophenone, 3-or 4- pentylacetophenone, 3'or 4-methoxyacetophenone, 3-or 4-bromocetophenone, 3-or 4-allylacetophenone, p-diacetylbenzene, 3 -or 4-methoxybenzophenone, 3-or 4-methylbenzophenone, 3- or 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4-chloro-4'-benzylbenzophenone, 3-chloroxanthone, 3,9 dichloroxanthone, 3-chloro-8-nonylxanthone, 3-methoxyxanthone, 3-iodo-7-methoxyxanthone, andthe like.

Also known are certain benzoin derivatives as are disclosed in German Patent No. F 52340 IVc/396. Many of these, while satisfactory, could'be improved upon. This invention discloses and claims coating compositions comprising a liquid vehicle, a colorant if desired and certain acetophenone compounds that show desirable properties when radiation cured by actinic or non-ionizing radiation means.

DESCRIPTION OF THE INVENTION In this invention novel coating or ink compositions are disclosed that are cured to dry products by nonionizing radiation at unexpectedly rapid rates. Applicants coatings comprise a liquid curable vehicle, a colorant, when a colored ink or coating is desired, and certain photosensitizers.

Thecolorants are well known and any of the conventional colorants can be used, including carbon black, titanuim dioxide, ultramarine blue, phthalocyanine green, phthalocyanine blue, phthalocyanine yellow, red pigments or dyes, or yellow, green, orange or any other color pigment or dye desired.

The liquid curable'vehicles are well known in the art and any one or mixture thereof can be used. These include the liquid polyesters, the liquid epoxy resins, the liquid vinyl resins, the liquid acrylyl resins, the liquid alkyd resins, or derivatives of the known radiation curable liquid resins. In some instances a curable solid resin can also be used by dissolving it in a solvent; such solutions are included within the meaning of the term liquid curable vehicle. In addition to the resins one can use the acrylated derivatives of the fatty acids or of the epoxidized fatty acids. These compounds are well known and the methods by which they can be producedare set forth in U.S. Pat. No. 3,l25,592, U.S. Pat. No. 3,224,989 and U.S. Pat. No. 3,256,225. In addition, the reaction products of the acrylated derivatives of the fatty acids with monoisocyanates (such as methyl isocyanate) or with polyisocyanates (such as tolylene diisocyanate) are also useful liquid curable vehicles. As previously indicated any of the liquid vehicles known to be useful in curable ink or coating compositions can be used. These are so well known in the art that extensive listing thereof is not necessary to enable one skilled in the art to practice the herein claimed invention.

. cyclohexylacetophenone, 'cyclopentylacetophenone,

The photosensitizer used to produce the compositions of this invention are certain acetophenone photosensitizers of the structure:

V v a wherein R is alkyl of from 1 to about 8 carbon atoms (methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tbutyl, pentyl, neopentyl, hexyl, heptyl, octyl, 2- ethylhexyl) or aryl of 6 ring carbon atoms (phenyl,

tolyl, xylyl, chlorophenyl, dichlorophenyl, methoxymethylacetophenone, 2,2-dipropoxy-2- hexylacetophenone 2 ,2-diphenoxy-2- ethylacetophenone 2 ,2-dimethoxy-2- 2,2-dipentoxy-2- 2,2di(2-ethylhexyl)-2- 2,2-diphenoxy-2- 2,2-di( nitrophenoxy)-2- cyclopentylacetophenone,

cyclopentylacetophenone, cyclohexylacetophenone.

Those compounds having the structural group in the molecule have not heretofore been known to be useful as photosensitizers in radiation curable coating compositions. It was found that these photosensitizers when added to the liquid vehicles produced compositions that did not gel on standing and that readily cured to tack-free films upon exposure to non-ionizing radiation. The fast rate of cure and freedom from gelling were completely unexpected and unobvious findings.

The acetophenone photosensitizers are readily produced by procedures that are known. For example, the 2,2-dialkoxy (or diaryloxy)-2-phenyl acetophenones can be produced by the reaction of benzil with the corresponding alkyl iodide or aryl iodide in dimethylformamide with barium oxide. This reaction is carried out at ambient temperatures as described by R. Kuhn and H. Trischmann, Chemische Berichte, Volume 94, page 2258. The 2,2-dialkoxy (or diaryloxy) acetophenones can be produced by the reaction of acetophenone with an alcohol in the presence of nitrosyl chloride as described in U.S. Pat. No. 2,995,573.

The concentration of acetophenone photosensitizer that can be present in the compositions of this invention can vary from 0.01 weight per cent to 20 weight per cent thereof; preferably from 0.1 weight per cent to weight per cent and most preferably from 1 weight per cent to 5 weight per cent. If desired other known photosensitizers and/or activators can also be present.

While we have indicated that any radiation curable liquid vehicle composition can be used it is understood that the compositions of this invention are a mixture of the radiation curable vehicle and the acetophenone photosensitizer defined above, with or without a pigment. The curable composition can contain a polymer dissolved or dispersed in a reactive monomer solution, a reactive polymer alone that can be cured by radiation, a reactive monomer alone that can be cured by radiation, or any of the above in admixture with an inert solvent as the liquid of vehicle. In addition to the acetophenone photosensitizers defined above one can additionally have present in the coating or ink composition any of the known photosensitizers or activators previously used in this field. The coating composition can also contain any of the conventional fillers, pigments, crosslinkers, wetting agents, flatting agents and other additives typically present in coating compositions. Many of these additives are known in the art and a detailed elaboration herein is not necessary to inform one skilled in the art as to their identity. Also, those skilled in the art are fully familiar with the concentrations of these additives suitable. The coating or ink compositions of this invention containing the acetophenone photosensitizers are cured by exposure to nonionizing radiation.

As a suitable source of non-ionizing radiation, one can use any source which emits radiation of from about 2,000 Angstroms to about 8,000 Angstroms, preferably from about 2,500 Angstroms to about 4,500 Angstroms. Suitable sources are mercury arcs, carbon arcs, tungsten filament lamps, xenon arcs, krypton arcs, sunlamps, lasers, and the like. All of these devices and sources are well known in the art and those familiar with the technology are fully aware of the manner in which the radiation is generated and the precautions to be exercised in its use.

Particularly efficient sources of non-ionizing light radiation for this invention are the ultraviolet mercury lamps and the swirl-flow plasma arc radiation arcs as described in U.S. Pat. No. 3,364,387. The apparatus or equipment necessary for generating the non-ionizing light radiation is not the subject of this invention and any source or apparatus capable of generating ultraviolet and visible light radiation can be used. The plasma arc emits non-ionizing high intensity predominantly continuum light radiation containing ultraviolet, visible and infrared light radiation that can be used to polymerize monomers and to crosslink polymer compositions in the initial step of the process of this invention. By means of proper light filters, one can selectively screen out a portion of the light radiation emitted permitting only that wavelength portion desired to reach the material that is being treated. The mercury lamps are known to emit ultraviolet light as the major light emission.

The term non-ionizing high intensity predominantly continuum light radiation means continuum radiation with radiance or source intensity of at least 350 watts per square centimeter steradian when integrated throughout the entire spectral range of said continuum light radiation (about 1,000 kilowatts per square foot of source projected area) having only a minor part of the energy in peaks of bandwidths less than 100 Angstrom units, with a positive amount up to about 30 per cent of the light radiated having wavelengths shorter than 4,000 Angstrom units and at least about per cent but less than all of the light energy radiated having wavelengths longer than 4,000 Angstrom units. This type of non-ionizing high intensity predominantly con tinuum light radiation is illustrated by the curves shown in FIGS. 1 to 3. These curves illustrate the non-ionizing high intensity predominantly continuum nature of the light radiation over the range of source intensity of from about 350 watts per square centimeter steradian to about 5,000 watts per square centimeter steradian. As is evident from the curves of FIGS. 1 to 3 the light radiated is predominantly continuum light with very little light emitted as line or peak radiation (band widths less than 100 Angstroms units). It is also evident from FIGS. 1 to 3 that less than about 30 percent of the light radiated has wavelengths shorter than 4,000 Angstroms and that at least about 70 per cent of the radiated light has wavelengths longer than 4,000 Angstrom units.

This form of light radiation is derived from an artificial source that generates non-ionizing high intensity predominantly continuum light radiation with a source intensity of at least about 350 watts per square centimeter steradian when integrated throughout the entire spectral range of said continuum light radiation, as abbreviated by the term: watts cm sr said nonionizing high intensity predominantly continuum artificial light radiation has at least about 70 per cent of the light radiated at a wavelength longer than 4,000 Angstroms and a positive amount less than about 30 per cent of the light radiated having a wavelength shorter than 4,000 Angstroms, generally at least about per cent of the light radiated has a wavelength longer than 4,000 Angstroms and a positive amount up to about 20 per cent of the light radiated has a wavelength shorter than 4,000 Angstroms, and it has a source intensity that can vary from about 350 watts (about 1,000 kilowatts per square foot of source projected area) to about 5,000 watts (about 15,000 kilowatts per square foot of source projected area) or more per square centimeter steradian when integrated throughout the entire spectral range. A convenient source of nonionizing high intensity predominantly continuum light radiation is a swirl-flow plasma are light radiation apparatus. The equipment for generating non-ionizing high intensity predominantly continuum light radiation by this means is known and available with many different forms thereof described in the literature.

While any artificial source of generating non-ionizing light radiation can be used, as previously indicated, the swirl-flow plasma arc radiation apparatus is most convenient. Hence, this source will be used in this application as illustrative of a means for obtaining the nonionizing high intensity predominantly continuum light predominantly continuum light radiation. The source of radiation in a 50 kilowatt swirl-flow plasma arc radiation source is an are that is only about four inches long and this is enclosed in a quartz envelope or lamp about 1.5 inches in diameter. This lamp or quartz envelope can be readily removed and refurbished and has an acceptably long lifetime. Further, a swirl-flow plasma are radiation apparatus having a 250-kilowatt rating would be only about two or three times as large as a 50- kilowatt source. Another advantage in the use of such equipment is the absence of a need for expensive radiation shielding. Precautions required for the artificial light sources include those needed to protect ones eyes from the intense light emitted and also to protect oneself from the ultraviolet light present to prevent inadvertent eye damage or sunburn effect on the body.

As is known, non-ionizing high intensity predominantly continuum light radiation from a swirlflow plasma are radiation source is emitted from an arc generated between a pair ofelectrodes that are lined up axially and encased in a quartz cylinder. In an embodiment a pair of concentric quartz cylinders between which cooling water'or gas flows is used. A rare gas, such as argon, krypton, neon or xenon, introduced into the inner cylinder tangentially through inlets located at one end of the inner cylinder, creates a swirling flow or vortex which restricts the arc to a small diameter. An electrical potential applied across the electrodes causes a high density current to flow through the gas to generate a plasma composed of electrons, positively charged ions and neutral atoms. A plasma generated in the above gases produces nonionizing high intensity predominantly continuum light radiation with diffuse maxima in the region of from about 3,500 to about 6,000 Angstroms. The radiation source can also be used with reflectors or refractive optical systems to direct the non-ionizing high intensity predominantly continuum light radiation emanating from the arc to a particular point or direction or geometrical area.

The non-ionizing high intensity predominantly continuum light radiation generated by a plasma are is a continuum rather than a peak or line radiation. As can be seen from the spectra of FIGS. 1 to 3 there is a continuum of radiation throughout the entire spectral range shown. This type of continuum radiation in the ultraviolet range has not heretofore been obtainable from the conventional commercial mercury arcs or lamps generally available for generating ultraviolet light. The previously known means for generating ultraviolet light produced light that shows a line or peak spectrum in the ultraviolet range, as exemplified by FIG. 4; it is not a continuum spectrum in the ultraviolet range. In a line spectrum the major portion of usable ultraviolet light is that portion at which the line or band in the spectrum forms a peak; in order to obtain maximum use of such energy the material or composition that is to be treated with ultraviolet radiation must be capable of absorbing at that particular wavelength range at which the peak appears. In the event the material or composition does not have the ability to absorb at that particular wavelength range there is little or no absorption or reaction. Thus, in the event the material or composition to be treated absorbs at a particular wavelength range in one of the valleys of the spectral curve there will be little or no reaction since there is little or no ultraviolet energy to adequately excite the system. With a non-ionizing high intensity predominantly continuum radiation, as is shown by FIGS. 1 to 3, there is a high intensity predominantly continuum radiation of ultraviolet energy across the entire ultraviolet wavelength range of the spectrum shown and there is generally sufficient ultraviolet energy generated at all useful ultraviolet wavelengths to enable one to carry out reactions responsive to ultraviolet radiation without the problem of selecting compounds that will absorb at peak wavelength bands only. With the non-ionizing high intensity predominantly continuum radiation one does not have the problem of being unable to react materials or compositions that absorb in the valley areas only since for all intents and purposes such valleys do not exist in non-ionizing high intensity predominantly continuum radiation, the high intensity radiated light energy is essentially a continuum it is not in peak bands.

FIG. 1 is the light radiation curve from an 18 kilowatt argon swirl-flow plasma arc radiation source. The measured source intensity of the light was 360 watts per square centimeter steradian; about 8 per cent of the light had a wavelength shorter than 4,000 Angstrom units and about 92 per cent of the light had a wavelength longer than 4,000 Angstrom units.

FIG. 2 is the light radiation from a kilowatt argon swirl-flow plasma arc radiation source. The measured source intensity was about 2,300 watts per square centimeter steradian; about 10 per cent of the light had a wavelength shorter than 4,000 Angstrom units and about per cent of the light had a wavelength longer than 4,000 Angstrom units.

FIG. 3 is the light radiation from a 71 kilowatt argon swirl-flow plasma arc radiation source. The measured source intensity was about 4,860 watts per square centimeter steradian; about 12 per cent of the light had a wavelength shorter than 4,000 Angstrom units and about 88 per cent of the light had a wavelength longer than 4,000 Angstrom units.

Non-ionizing high intensity predominantly continuum light radiation as shown by FIGS. 1 to 3 is to be distinguished from the low intensity ultra-violet radiation generated by commercially available low, medium and high pressure mercury arc ultraviolet lamps. These mercury arc lamps produce light emission which is primarily line or peak rather than continuum light. FIG. 4 is a typical curve for the light radiation from a mercury arc lamp. As shown in FIG. 4, a major part of the light appears in bands or peaks narrower than Angstrom units, and much less than 70 per cent is emitted at wavelengths above 4,000 Angstrom units. Such line or peak ultraviolet light radiation is also suitable in the processes of this invention.

The irradiation can be carried out in air or under an inert gas atmosphere such as nitrogen, carbon dioxide, helium, neon, argon, etc. It is preferably conducted under an inert gas since air or oxygen tends to inhibit the curing reaction. The following examples further to serve to describe the invention:

EXAMPLE I A coating composition was prepared using 50 grams of a commercial polyester having internal unsaturation (Co Resyn I), 30 grams of 2-hydroxyethyl acrylate and 20 grams of neopentylglycol diacrylate. Two weight per cent concentrations of different photosensitizers were added to separate aliquots of the composition and then applied to No. 37 Bonderite steel panels at a wet film S ivai-dhardness Acetone Photosensitizer & glass 100 resistance, sec.

2,2-dimethoxy-2 phenylacetophenone i 46 135 2,2-dimethoxyacetophenone 26 1,099 benzoin tacky mixture of n-butyl and isobutyl ethers of benzoin y Sward hardness Photosensitizer 1.2 seconds 2 seconds 2,2-dimethoxy-2-phenylacetophenon 34 2.2-dicthoxyacetophenone 26 28 2,2-dimethoxyacetophenone I6 32 benzoin l4 l8 mixture of n-butyl and isobutyl ethers of benzoin 24 26 These results show the general improvements of the acetophenones as compared to the benzoins in hardness properties of the films.

" 1 W EYE/1W A coating composition was prepared bydissolving 70 grams of the same polyester used in Example 1 in 30 grams of styrene and then two weight per cent of various photosensitizers was added to aliquots thereof and coated on No. 37 Bonderite steel panels. The coated 8 aaas'weieiasaared in air dribed means 1. The results clearly established the superiority of 2,2- dimethoxy-Z-phenylacetophenone over the conventional benzoin photosensitizers. As shown, the benzoin photosensitizers produce tacky films as compared to dry fully cured films when using 2,2-dimethoxy-2- phenylacetophenone.

4 second exposure 8 second exposure Sward Acetone Sward Acetone Photosensitizer hardness resishardness resistance,

tance, sec sec 12,2;quEm2u-2; a o V 4 phenylacetophenone 22 224 44 519 benzoin tacky 26 232 mixture of n-butyl tacky I8 442 and isobutyl ethers of benzoin EXAMPLE 3 A 100 per cent solids coating composition was prepared by dissolving 50 grams of acrylated epoxidized soyabean oil in 30 grams of 2-hydroxyethyl acrylate and 20 grams of neopentylglycol acrylate. Different photosensitizers were added to aliquots of this composition at a concentration of 0.1 molal and each was applied to No. 37 Bonderite steel panels at a wet film thickness of two mils. The coated panels were then exrz if sl sssseqsta firsx light as s sr in Example 1. The data show the overall improvement obtained by the use of the photosensitizers of tms invention; the particularly outstanding results of 2,2- dimethoxy-Z-phenylacetopheone are clearly apparent.

. 40 Sward Acetone Photosensitizer hardness resistance sec 2,2-dimethoxy-2- phenylacetophenone I8 70 2,Z-dimethoxyacetophenone I6 55 benzoin 12 benzoin acetate 0 non cured EXAMPLE 4 The same coating composition described in Example 3 was cured by exposure to the non-ionizing high intensity predominantly continuum light radiation emanating from an argon 7 S-kilowatt plasma arc radiation source. Exposure was at a distance of about 4 feet from the arc. The composition containing the 2,2-dimethoxy-2-phenylacetophenone photosensitizer showed curing within 0.12 second, whereas none of the controls did; after 0.25 second it was still better than any 0 of the benzoin controls.

Exposure Time 0. l 2 0. l 7 0.25 Sward Acetone Sward Acetone Sward Acetone hardness resistance, hardness resistance, hardness resistance Photosensitizer sec. sec sec 2,2-dimethoxy-2- phenylacetophenone 4 25 10 25 I6 45 benzoin 0 0 4 l 5 I4 30 i /(me amine? Exposure Time 0.12 0.11 0.25 Sward Acetone Sward Acetone Sward Acetone hardness resistance, hardness resistance, hardness resistance Photosensitizer sec. sec sec benzoin acetate 0 0 O f) 0 benzoin n-butyl ether 0 0 4 l0 8 20 benzoin isobutyl ether 0 0 6 l0 6 25 EXAMPLE 5 position gelled during themixingprocess. This is not This example shows the use of the photosensitizers in the polymerization of acrylyl monomers. In this use, the 2,Z-dimethoxy-2-phenylacetophenone class of compounds is superior to the 2,2-dialkoxyacetophenones even though these latter are also good. A solution of 5 grams of methyl methacrylate in 5 ml of benzene and containing 0.01 gram of the photosensitizer was placed in a test tube and sealed. The irradiation was carried out with the sealed tubes placed on a rotating carriage located about threeinches interior of a circle of 16 Rayonet RPR-3,500 mercury lamps, each lamp rated at about [.6 watts. The circle of mercury lamps had a diameter of about 12 inches. This equipment is available commercially as the Rayonet RPR-l00 Reactor from the Southern New England Ultraviolet Co., Middletown, Conn. The irradiation was carried out at ambient temperatures for 90 minutes. The reaction mixture was then poured into 50 ml. of hexane and the poly(methyl methacrylate) was filtered, dried and weighed, it was a white powder. The yields are shown below:

Yield Photolenlltlzer g 2,Z-dimethoxy-Z-phenylncetophenone 4.40 88.0 2,Z-dimethoxyscetophenonc 3.25 65.0 2,2-diethoxyacetophenone 3.08 60.1

EXAMPLE 6 A white-pigmented ink composition was produced by .milling 40 parts of acrylated epoxidized soybean oil, 10

parts of pentaerythritol triacrylate and 50 parts of titanium dioxide on a three-rollmill. To portions of this white ink there wereadded various photosensitizers at a concentration of five weight per cent and uniformly blended therein. The inks were then applied to steel panels with a rubber ink roller at a film thickness of about 0.4 mil and irradiated by exposure to light radiation from two 2.2 kilowatt mercury vapor lamps at a distance of about lOinches. The results are shown below:

diisopropoxyacetophenone remained fluid and did not gel on standing; they cured to a tack-free state rapidly on irradiation to yield a commercially acceptable film coating. The attempt to produce a composition by the addition of benzoin was not successful since the comacceptable commercially. Benzoin butyl ether formed a composition which gelled on standing at room temperature for several hours, also unacceptable; and as seen from the data the radiation period required to obtain a tack-free film was from 67 per cent to 250 per cent longer. The substitution of acrylated epoxidized linseed oil or the reaction product of methyl isocyanate or tolylene diisocyanate with acrylated epoxidized soybean oil or with acrylated epoxidized linseed oil for the acrylated epoxidized soybean oil in the composition yields similar results.

EXAMfiLE 5 A black-pigmented co nposition was produced as described in Example 6 using 40 parts of acrylated epoxidized soybean oil, 10 parts of pentaerythritol triacrylate and 10 parts of carbon black. After addition of the photosensitizers the compositions were applied to steel panels and cured as in Example 6, with the following results:

Photosensitizer Exposure Time Results 2.2-dleth0xy- 42 seconds tuck-free acctophenone 2,2-diisopropoxy- 42 seconds lack-free scetophenone benzoin butyl ether benzoin The composition containing the 2,2- diethoxyacetophenone and the 2,2-

diisopropoxyacetophenone remained fluid and gel free on standing; they readily cured to a tack-free state on irradiation to yield commercially acceptable film eoatings. As iii Example 6; the attempt to addbenzoin to the composition caused gelation during the mixing-pro cess. The ink composition containing the benzoin butyl ether also gelled immediately after the addition of the fertilizer. The substitution of neopentyl glycol diacrylate for the pentaerythritol triacrylate in the composition yields similar results.

EXAMPLES A blue-pigmented coating composition was produced as described in Example 6 using 40 parts of acrylated epoxidized soybean oil, 10 parts of pentaerythritol triacrylate and 30 parts of ultramarine blue. After addi- Mh phpt sssi izers thanks were... pplie t steel panels and cured as in Example 6, with the benzoin the attempt to add benzoin to th e composition caused gelation during the mixing process. The composition containing the benzoin butyl ethe'r gelled on standing at room temperature for several hours, and as seen from the data this composition required a longer radiation period to obtain a tack-free film.

The data shows that pigmented ink or coating compositions containing the defined acetophenone photosensitizers cure to a tack-free state in a much shorter period of time and that such compositions remain fluid and gel-free on standing whereas the same compositions with other photosensitizers require alonger cure time andgel either during mixing or on standing.

A composition was produced as described in Example :6 u si n g 50 parts of acrylated epoxidized soybean oi l and 0 parts of titanium dioxide. After addition of the photosensitizers the ink or coating compositions were applied to steel panels and cured as in Example benzoin methyl ether gelled during addition .E.X+$MP!:E 9 A composition was produced as described in Example 6 using 50 parts of acrylated epoxidized linseed oil ass 50 parts of titanium dioxide. After addition of the photosensitizers the inks were applied to steel panels and cured as in Example 6, with the following results:

Photosensitizer Exposure Time Result 2,2-diethoxyacetophenone 12 seconds tack-free 2,2-diisopropoxy- 12 seconds tack-free acetophenone 2,2-diethoxy-2- l2 seconds tack-free phenylacetophenone benzoin methyl ether l8 seconds tack-free What is claimed is: 1. A composition comprising a liquid curable vehicle and a photosensitizer of the formula:

wherein R is alkyl of from 1 to 8 carbon atoms or aryl of 6 ring carbon atoms and B is hydr gen alkyl of 6161 to 8 carbon atoms, aryl of from 6 to 14 carbon atoms or cycloalkyl of 5 to 8 ring carbon atoms, said photosensitizer being present in said composition at a concentration of from 0.01 to 20 weight percent.

2. A composition as claimed in claim 1 wherein the vehicle is acrylated epoxidized soybean oil.

3. A'composition as claimed in claim 1 wherein the vehicle is acrylated epoxidized linseed oil.

4. A composition as'claimed in claim 1 wherein the vehicle is the reaction product of methyl isocyanate with acrylated epoxidized soybean oil.

5. A composition as claimed in claim 1 wherein the vehicle is the reaction product of methyl isocyanate with acrylated epoxidized linseed oil.

6. A composition as claimed in claim 1 wherein the vehicle is the reaction product of tolylene diisocyanate with acrylated epoxidized soybean oil.

7. A composition as claimed in claim 1 wherein the vehicle is the reaction product of tolylene diisocyanate with acrylated epoxidized linseed oil.

8. A composition as claimed in claim 1 wherein the photosensitizer is 2,2-diethoxyacetophenone.

9. A composition as claimed in claim 2 wherein the photosensitizer is 2,2-diethoxyacetophenone.

10. A composition as claimed in claim 3 wherein the photosensitizer is 2,2-diethoxyacetophenone.

11. A composition as claimed in claim 4 wherein the photosensitizer is 2,2-diethoxyacetophenone.

12. A composition as claimed in claim 5 wherein the photosensitizer is 2,2-diethoxyacetophenone.

13. A composition as claimed in claim 6 wherein the photosensitizer is 2,Z-diethoxyacetophenone.

14. A composition as claimed in claim 7 wherein the photosensitizer is 2,2-diethoxyacetophenone.

15. A composition as claimed in claim 1 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.

16. A composition as claimed in claim 2 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.

17. A composition as claimed in claim 3 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.

18. A composition as claimed in claim 4 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.

19. A composition as claimed in claim 5 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.

20. A composition as claimed in claim 6 wherein the photosensitizer is 2,Z-diisopropoxyacetophenone.

21. A composition as claimed in claim 7 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.

22. A composition as claimed in claim 1 additionally comprising a pigment.

23. A composition as claimed in claim 22 wherein the pigment is titanium dioxide.

24. A composition as claimed in claim 2 additionally comprising a pigment.

25. A composition as claimed in claim 3 additionally comprising a pigment.

26. A composition as claimed in claim 4 additionally comprising a pigment.

27. A composition as claimed in claim 5 additionally comprising a pigment.

28. A composition as claimed in claim 6 additionally comprising a pigment.

29. A composition as claimed in claim 7 additionally comprising a pigment.

30. A composition as claimed in claim 8 additionally comprising a pigment.

31. A composition as claimed in claim 9 additionally comprising a pigment.

32. A composition as claimed in claim 10 additionally comprising a pigment.

33. A composition as claimed in claim 11 additionally comprising a pigment.

34. A composition as claimed in claim 12additionally comprising a pigment.

35. A composition as claimed in claim 13 additionally comprising a pigment.

36. A composition as claimed in claim 14 additionally comprising a pigment.

37. A composition as claim in claimed 15 additionally comprising a pigment.

38. A composition as claimed in claim 16 additionally comprising a pigment.

39. A composition as claimed in claim 17 additionally comprising a pigment.

40. A composition as claimed in claim 18 additionally comprising a pigment.

41. A composition as claimed in claim 19 additionally comprising a pigment.

42. A composition as claimed in claim 20 additionally comprising a pigment.

43. A composition as claimed in claim 21 additionally comprising a pigment.

44. A composition as claimed in claim 31 wherein the pigment is titanium dioxide.

45. A composition as claimed in claim 32 wherein the pigment is titanium dioxide.

46. A composition as claimed in claim 38 wherein the pigment is titanium dioxide.

47. A composition as claimed in claim 39 wherein the pigment is titanium dioxide. 

2. A composition as claimed in claim 1 wherein the vehicle is acrylated epoxidized soybean oil.
 3. A composition as claimed in claim 1 wherein the vehicle is acrylated epoxidized linseed oil.
 4. A composition as claimed in claim 1 wherein the vehicle is the reaction product of methyl isocyanate with acrylated epoxidized soybean oil.
 5. A composition as claimed in claim 1 wherein the vehicle is the reaction product of methyl isocyanate with acrylated epoxidized linseed oil.
 6. A composition as claimed in claim 1 wherein the vehicle is the reaction product of tolylene diisocyanate with acrylated epoxidized soybean oil.
 7. A composition As claimed in claim 1 wherein the vehicle is the reaction product of tolylene diisocyanate with acrylated epoxidized linseed oil.
 8. A composition as claimed in claim 1 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 9. A composition as claimed in claim 2 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 10. A composition as claimed in claim 3 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 11. A composition as claimed in claim 4 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 12. A composition as claimed in claim 5 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 13. A composition as claimed in claim 6 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 14. A composition as claimed in claim 7 wherein the photosensitizer is 2,2-diethoxyacetophenone.
 15. A composition as claimed in claim 1 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 16. A composition as claimed in claim 2 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 17. A composition as claimed in claim 3 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 18. A composition as claimed in claim 4 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 19. A composition as claimed in claim 5 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 20. A composition as claimed in claim 6 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 21. A composition as claimed in claim 7 wherein the photosensitizer is 2,2-diisopropoxyacetophenone.
 22. A composition as claimed in claim 1 additionally comprising a pigment.
 23. A composition as claimed in claim 22 wherein the pigment is titanium dioxide.
 24. A composition as claimed in claim 2 additionally comprising a pigment.
 25. A composition as claimed in claim 3 additionally comprising a pigment.
 26. A composition as claimed in claim 4 additionally comprising a pigment.
 27. A composition as claimed in claim 5 additionally comprising a pigment.
 28. A composition as claimed in claim 6 additionally comprising a pigment.
 29. A composition as claimed in claim 7 additionally comprising a pigment.
 30. A composition as claimed in claim 8 additionally comprising a pigment.
 31. A composition as claimed in claim 9 additionally comprising a pigment.
 32. A composition as claimed in claim 10 additionally comprising a pigment.
 33. A composition as claimed in claim 11 additionally comprising a pigment.
 34. A composition as claimed in claim 12 additionally comprising a pigment.
 35. A composition as claimed in claim 13 additionally comprising a pigment.
 36. A composition as claimed in claim 14 additionally comprising a pigment.
 37. A composition as claim in claimed 15 additionally comprising a pigment.
 38. A composition as claimed in claim 16 additionally comprising a pigment.
 39. A composition as claimed in claim 17 additionally comprising a pigment.
 40. A composition as claimed in claim 18 additionally comprising a pigment.
 41. A composition as claimed in claim 19 additionally comprising a pigment.
 42. A composition as claimed in claim 20 additionally comprising a pigment.
 43. A composition as claimed in claim 21 additionally comprising a pigment.
 44. A composition as claimed in claim 31 wherein the pigment is titanium dioxide.
 45. A composition as claimed in claim 32 wherein the pigment is titanium dioxide.
 46. A composition as claimed in claim 38 wherein the pigment is titanium dioxide.
 47. A composition as claimed in claim 39 wherein the pigment is titanium dioxide. 